India is fourth largest energy consumer in the world. Energy consumption in India has doubled in last decade. Potential hydrate deposits have been found in Andaman-Nicobar Island, Krishna Godavari basin, Konkan and Kutch offshore. A reliable assessment of the feasibility of producing natural gas from the earth's naturally occurring hydrates requires several pieces of key information. The specific challenges encountered for methane recovery from gas hydrates are as follows:                1. Cost of operation        2. Scalability of operation        3. Faster hydrate dissociation kinetics        
The thermodynamics of such systems is fairly well understood, and thus methane recovery through hydrate dissociation can be achieved by maintaining a certain temperature/pressure gradient in and around the hydrate bearing sediment (several meters below sea level). The higher temperature gradient required, the more difficult and expensive is the process. Introduction of suitable additives (in low doses) to the system which can potentially change the thermodynamic boundary would allow reduction in working temperature thus would be beneficial economically. These additives would interact with the hydrogen bonds or create defects in the ice like hydrate crystals, enabling an enhanced hydrate dissociation rate at relatively lesser temperature gradient. The other factor that needs to be kept in mind while identifying the additives discussed earlier is their potential impact on the environment. Although gas hydrates are known to occur in marine sediments around the world, little is known about the technology necessary to recover gas from gas hydrates. The three primary processes currently being deliberated upon when it comes to recovery of gas from gas hydrates are a) Thermal Stimulation, b) Depressurization and c) Additive Injection. Individually, though effective, these methods have their own unique disadvantages which make the hydrate dissociation process highly uneconomical and cumbersome. Some work combining the depressurization and thermal stimulation methods and the resultant of the same has been observed to enhance hydrate dissociation kinetics compared to the individual processes. It is expected that a mature process using a combination of all the three approaches will be ideal to optimize the operational costs. The addition of certain chemicals in small amounts which may enhance hydrate dissociation (methane recovery) rate without having any toxic effects on the environment has caught the imagination of researchers worldwide although research focussing on this subject is still in its infancy.
Article titled ‘Natural gas production from hydrate decomposition by depressurization” by C Jia et al. published in Chemical Engineering Science, 2001, 56, pp 5801-5814 reports natural gas production from the decomposition of methane hydrate in a confined reservoir by a depressurizing well. For different well pressures and reservoir temperatures, distributions of temperature and pressure in the porous layer of methane hydrate and in the gas region are evaluated.
U.S. Pat. No. 5,713,416 discloses a method of decomposing gas hydrates and releasing natural gas and water which involves combining a liquid (acid) with another liquid (base) which would react exothermically with each other to form a hot salt solution and subsequently contacting said gas hydrates with said hot salt solution.
U.S. Pat. No. 6,214,175 discloses a method for recovering gas by dissociating gas hydrates comprising the steps of: (a) providing the gas hydrate within an occupying zone; (b) positioning a source of electromagnetic radiation within the said gas hydrate occupying zone; and (c) recovering gas from said gas hydrates by applying electromagnetic radiation from the electromagnetic radiation source of step (b) to the gas hydrates at a frequency within the range of: from direct current to visible light, at energy density sufficient to dissociate the gas hydrates to evolve its constituent gas.
U.S. Pat. No. 7,879,767 disclosed An aqueous, viscoelastic fluid gelled with a viscoelastic surfactant (VES) is inhibited against hydrate formation with an effective amount of an additive that could be one or more halide salts of alkali metals and alkali earth metals, formate salts, alcohols, glycols, glycol amines, sugars, sugar alcohols, amidoamine oxides, polymers such as polyamines, polyvinylpyrrolidones and derivatives thereof, polyvinyl alcohols and derivatives thereof, polycaprolactams and derivatives thereof, hydroxyethylcellulose, and mixtures thereof. These fluids are inhibited against hydrate formation and may have increased viscosity as well. The additives may increase viscosity to the point where less VES is required to maintain a given viscosity. These inhibited, aqueous, viscoelastic fluids may be used as treatment fluids for subterranean hydrocarbon formations, such as in stimulation treatments, e.g. hydraulic fracturing fluids. The additive is soluble in the fluid and may be a halide salt of an alkali metal and/or an alkali earth metals, formate salts, alcohols, glycols, sugars, sugar alcohols, glycol amines, amidoamine oxides, polyamines, polyvinylpyrrolidones and derivatives thereof, polyvinyl alcohols and derivatives thereof, polycaprolactams and derivatives thereof, hydroxyethylcellulose, and mixtures thereof.
Article titled “Effects of biosurfactants on gas hydrates” by Amit Arora et al. published in Journal of Petroleum & Environmental Biotechnology 2014, 5:2 reports the effects of biosurfactants such as Rhamnolipid, Surfactin, Snomax, Emulsan, Phospholipids, Hydroxystearic acid etc. on Gas Hydrate formation.
Article titled “Methane Index: A tetraether archaeal lipid biomarker indicator for detecting the instability of marine gas hydrates” by Yi Ge Zhang et al. reports a molecular fossil proxy, i.e., the “Methane Index (MI)”, to detect and document the destabilization and dissociation of marine gas hydrates. MI consists of the relative distribution of glycerol dibiphytanyl glycerol tetraethers (GDGTs), the core membrane lipids of archaea. The rational behind MI is that in hydrate-impacted environments, the pool of archaeal tetraether lipids is dominated by GDGT-1, -2 and -3 due to the large contribution of signals from the methanotrophic archaeal community. This study in the Gulf of Mexico cold-seep sediments demonstrates a correlation between MI and the compoundspecific carbon isotope of GDGTs, which is strong evidence supporting the MI-methane consumption relationship. Preliminary applications of MI in a number of hydrate-impacted and/or methane-rich environments show diagnostic MI values, corroborating the idea that MI may serve as a robust indicator for hydrate dissociation that is useful for studies of global carbon cycling and paleoclimate change.
Not much work has been done on dissociation of gas hydrates and there is a dearth of data in literature regarding the same. It is however imperative to thoroughly study dissociation of gas hydrates because of the different parameters involved in the hydrate dissociation process which need to be monitored and the potential challenges to be faced during hydrate dissociation in field scale operations.
Therefore, there is a real need at the moment for a process for dissociation of gas hydrates which will be ideal to optimize the operational costs. Accordingly, the present inventors find that the presence of a small amount of certain additives in the system in conjunction with changing the temperature and pressure conditions of the hydrate bearing sediment can significantly boost hydrate dissociation kinetics. These additives interact with water, forming hydrogen bonds and thus enhancing the rate of hydrate dissociation.